It is known that many thermoplastic polymer packaging materials, such as films, coatings, sheets, bags, and the like, with suitable strength and flexibility are used to enclose perishable foods, fruits, raw meats, daily dishes and vegetables. These packaging materials tend to discolor and fog during extended storage. Because of this, polymer packaging materials have to possess the following characteristics: (1) suitable thickness and cohesive properties for packaging, (2) high antifogging properties, i.e. the films do not accumulate water droplets on the surface of the material, (3) high mechanical strength at break, (4) appropriate slip properties, (5) excellent optical characteristics, such as gloss and transparency, and (6) sealability under heat.
There is a high demand in the packaging food industry, agriculture, industrial markets, flower wrapping trade, and the like for biaxially oriented thin antifogging films of different types that can be used for both food-wrapping and agricultural applications. The antifogging and antimicrobial films reduce the growth of living contaminants (such as bacteria and molds) and ensure that any condensation of water vapor occurs as an uniform, invisible, layer of water rather than as a series of individual droplets which are not only aesthetically undesirable but produce damaging effects.
The several goals of these films are: (1) to ensure that the polymer thin films retain their transparency so that the packaged contents are clearly visible and so that there is maximum light transmission into the enclosure, (2) to protect the packaged food products from undesired degradation that may be caused by the droplets of water, (3) to prevent large drops of condensed water from falling onto young plants, increasing the possibility of damage and disease, (4) to prevent plant “burning” caused by large drops of water lensing (concentrating and focusing) solar radiation onto the contents of the package, (5) to provide antimicrobial properties and (6) to provide prolonged shelf life by preventing the growth of the certain bacteria.
Currently, antifogging films (also known as antifog or antimist films) are produced by adding or coating various types of organic antifogging additives, such as ethoxylated sorbitan ester, glyceride fatty acid ester, glycerol stearate (or monostearate), glycerol oleate and sorbitan ester, and the like, to conventional film forming polymers, such as polyolefins, flexible vinyl chloride polymers, oriented styrene polymers, polyesters, ethylene-vinyl acetate copolymers, and the like.
There are a number of available patent publications related to antifogging polymer films obtained by using different types of thermoplastic film-forming/antifogging additives as discussed below. These patents relate to systems such as a biaxially stretched film with a base of an olefin polymer resin composition containing ethylene-propylene copolymer and 0.5% of polyethylene glycol stearyl ether, olefin polymer/fatty acid monoester of polyhydric alcohol (or alkaline metal salt of a diester of sulfosuccinic acid), polyolefin/ethylene oxide (or monoglyceride of a fatty acid), polystyrene/alkyl phenyl polyethylene glycol ether (of fatty alcohol sulfate) base coating, polyethylene/polyhydric alcohol esters or metal salts of either saturated or unsaturated monocarboxylic fatty acids, ethylene polymer and polybutene blend/glyceride with acyl group, and ethylene-acrylic acid (or ethyl acrylate and/or vinyl acetate) copolymers or low density ethylene polymers/alkyl phenyl polyethylene glycol ethers or alkoxylated alkyl phenol. But all of these patents suffer from one or more of the following disadvantages such as higher haze values, low values of sheen, higher transverse or longitudinal shrinkage, and poor antifogging properties.
More specifically, in U.S. Pat. No. 4,066,811, there is disclosed raw tubular polyolefin films with suitable orientation determined by heat shrinkage, containing ethylene-vinyl acetate copolymer, polyethylene, polypropylene or mixtures thereof, polyalkylene ether polyol and non-ionic surfactant-polyhydric alcohol ester derivatives of fatty acids. In the above patent, the determination of antifogging properties of the subject film was according to the following measurements: (1) no water droplets were present on the surface and water was in a uniform layer, (2) large water droplets locally were adhered or there was unevenness in the state of any adhering water droplets, and (3) fine water droplets adhered to the whole surface.
Other recently published patented inventions, such as JP Pat. 09-104,092, relate to various polymer compositions, sheets, and films having fog resistant properties. Disclosed therein are antifogging sheets comprising weather-resistant polycarbonate based films, hot-melt poly(methylmethacrylate) films containing a benzotriazol UV-absorber, and cellulose films containing a diethyl phthalate plasticizer, to form a flat or wavy laminated panel allegedly providing good weather and moisture resistant adhesion.
Antifogging polypropylene lids with smooth handling properties, such as disclosed in JP Pat. 09-76,339, were prepared by thermal formation of polypropylene sheets, where the interior faces of the lids exhibit antifogging property and the exterior faces have a friction coefficient of 0.01-0.7. The plastic of these lids was stretched in the machine direction, coated on the exterior face with poly(dimethylsiloxane) and on the interior face with sugar fatty ester emulsion, and thermal formed into a lid showing no noise when removed from their stack.
Plastic sheets having anisotropic surface characteristics, including fogging and adhesion properties, are disclosed in JP Pat. 09-85,847 and comprise alternating strips of nylon 6-12 and ethylene-methacrylic acid copolymer.
There are antifogging laminated films for agricultural uses that use a polyolefin resin middle layer. This layer frequently consists of high density polyethylene and synthetic rubber with external layers consisting of antifogging agents. One laminate, disclosed in JP Pat. 0994,930, comprises an ethylene-vinyl acetate copolymer middle layer, uses KFG 561 as an antifogging agent, and showed good blocking resistance, mechanical strength and fogging presentation (45° C. water for 45 days or 0° C. environment and 20° C. water for 24 hours).
Other agricultural antifogging films, such as the ones disclosed in JP Pat. 09-95,545, were prepared using olefin copolymer compositions containing sulfonated olefin copolymers, ethylene-C3-12 olefins, and ethylene-acrylic copolymers. The olefin copolymers were synthesized by polymerization of olefins in the presence of metallocene (Zr) catalyst containing silica and methylaluminoxane. More specifically, a transparent antifogging film was prepared from a mixture of 80% sulfonated olefin polymer (reaction product of butane sulfonate with ethylene-acrylic copolymer) and 20% of ethylene-hexene-1 copolymer which was polymerized in the presence of a catalyst system containing silica, methylaluminoxane, bis(1,3-n-butylmethyl cyclopentadienyl)zirconium dichloride and triisobutylaluminum.
JP Pat. 09-77,938 discloses a polymer composition with good sliding properties that comprises 10-60% of graft copolymers manufactured by grafting an elastomer with ≧1 layers of antifogging agent KFG 561. The resultant laminate used ethylene-vinyl alcohol copolymer as a middle layer, 20% of hydrogenated butadiene-styrene elastomer as an inner layer, and 10% of the said elastomer outer layer comprises a fire retardant agent and showed good blocking resistance, mechanical properties, dust, and fogging presentation.
Fluoropolymer films with wetting ≧35 dyn cm, as disclosed in JP Pat. 09-136,980, were mixed with antifogging agents comprising water-thinned acrylic polymer emulsions, such as ethyl acrylate-2-hydroxyethylmethacrylate-2-hydroxymethacryloxybenzophonone-methyl methacrylate copolymer, and colloidal SiO2. Films prepared according to this patent showed reasonably good antifogging property for 7 months.
Two Japanese patent inventions, JP Pat. 09-165,178 and JP Pat. 09-165,447, disclose heat-aging and light-resistant propylene polymer compositions causing no fogging of glass for use in automotive interiors. These compositions contain (A) crystalline polypropylene, (B) inorganic filler, such as TiO2, (C) ethylene-propylene elastomer, and (D) conventional stabilizers, antioxidants, antiblocking agents, and other additives such as epoxy resins, hydroxyl-containing low molecular weight polyolefins, polyethylene waxes, and anionic surfactants. Plates prepared from this composition by kneading, pelleting, and injection molding show 150° C. oven life for 320 hours. The plate and glass plate were left in a sealed container at 120° C. for 20 hours and showed a haze of the glass of 0.8%.
In another patent entitled “Fog-Resistant Heat-sealable Film”, U.S. Pat. No. 4,341,825, there is disclosed a transparent, heat-sealable, laminated film that has a first layer of a difficulty heat-sealable polymer, such as an axially oriented polyethylene terephthalate film with 0.002-0.006 cm thickness, and a second layer of a readily heat-sealable polymer, such as low density polyethylene and copolymers of ethylene with acrylic acid, ethyl acrylate and vinyl acetate, chemically interfacially joined to the first film layer. The said second film layer comprises 0.2-0.7% of an alkyl phenyl polyethylene glycol ether of the formula, R—C6H4—O—(CH2)nOR′—OH, where R-alkyl C10-15 and alkylene C4-10 as an antifogging agent. The resulting laminated film is then heated to 130° C. and exposed to UV-light through the second film layer for a time and at an intensity sufficient to cause the formulation of the chemically interfacial bond between the two layers. The film obtained resists the formation of fog when utilized to package refrigerated foods. However, the disadvantages of this invention can be noted as the following: (1) the subject film comprises two layers containing non-oriented ethylene polymers, (2) the subject film has a high thickness, (3) the subject film has a high content of antifogging agents as compared with more conventional polymer fog-resistant films, and (4) the antifogging agents used in the subject film were synthesized by reaction of alkyl phenol with polyethylene oxides. In this case, the trace of the phenol will be present in the product synthesized. This can limit the use of this specific additive in the food packaging industry.
Another patent, entitled “Fog-Resistant Olefin Polymer Films”, U.S. Pat. No. 4,486,552, discloses a film-forming composition for making packaging films that are resistant to fogging, especially when employed as a packaging film for moist products. The subject film of this patent comprises an ethylene polymer, especially a linear low density polyethylene, and 0.5-2.0% of antifogging agents, such as an ethoxylated alkyl phenol along with a mixed mono-, di-, and/or triglyceride, a polyoxyalkylene fatty acid ester or various combinations of said additives. The mixing of the antifogging agents into the ethylene polymers, which can be LDPE, LLDPE, HDPE, ethylene-octene-1, or blends or alloys of said olefin polymers, is done by mixing the antifogging agents into molten polymer by commonly used techniques, such as roll-milling, mixing in a Banbury type mixer, mixing in an extruder barrel, or the like. The subject film was formulated as 0.015 mm on a cast film unit at 260° C. melt temperature and chill roll temperature of 18° C. It is noted that the films prepared according to this patent have a relatively high fog resistance when compared with commercially available plasticized poly(vinyl chloride) films, such as the one disclosed in U.S. Pat. No. 4,072,790. Further, other high qualities are produced, such as improved transparency (64.3 against 5.0 for PVC), gloss (95.9 against 89.0), haze (1.0% against 2.0%), lower heat seal range (121-127° C. against 149-177° C.), and overall toughness, as compared to PVC films. However, it was shown that the antifogging agents used in this patent exude to the surface of the film within approximately 48 hours after fabrication. The subject films of this patent have the following disadvantages: (1) the films are not multi-layered and biaxially oriented, (2) the films have a high thickness and high density resulting in a low yield, (3) there is a low heat-sealing temperature, (4) there are low values of surface and mechanical characteristics, the film surfaces are not treated by corona discharge, and (5) the film comprises relatively high concentrations of antifogging agents used in the polymer composition.
U.S. Pat. No. 4,876,146 and 4,956,209, disclose “Anti-fogging Multi-layered Film and Bag Produced Therefrom for Packaging Vegetables and Fruits”. These patents describe biaxially oriented and multilayered antifogging polyolefin films useful for packaging fresh vegetables and fruits comprising: (A) a 4-100 μm base layer formed from polypropylene or ethylene-(5%)-propylene copolymer or ethylene-vinyl acetate (acrylic acid or styrene) copolymer; and (B) one or two surface layers that are 0.3-8.0 μm thick and having heat-sealable properties resulting from a (1:1) mixture of propylene-butene-1 (18%) and ethylene (3.5%)-butene-1 copolymers containing 0.3-3.0% antifogging agent such as higher fatty acid ester of monoglyceride (or alkyldialcoholoamide, polyalkylene glycol, polyalkylene glycol alkylphenol ether). There are also other conventional additives, such as antistatic and lubricating agents. In accordance with said patent it is possible to incorporate the antifogging agent only in a base layer of the film so that the antifogging agent migrates to and diffuses into the surface layer(s) after laminating the layers. This migration and incorporation of the antifogging agents into the surface layers provides the antifogging property important to the surface layer. Antifogging properties were observed, the film was formed as a bag and “Shtitake” mushroom were enclosed in the bag; the temperature was varied twice per day with a rise and drop between 20 and 40° C.; the result was observed after 1 day. There was little fogging, discoloration, and the measured surface tensions were 38-42 dyne/cm. The disadvantages of the films prepared in accordance with said patent included: (1) high values of haze (3.1%), (2) low values of sheen (86.6%), (3) coloring agent in the film does not comply with food contact standards of the U.S. FDA, (4) the identification of fogging properties used a non-effective method, (5) the films had low performances as antifogging surfaces, i.e. discontinuous film of water is observed on the surface, (6) E-P-B terpolymer is not used in the surface layers, (7) ethylene-vinyl acetate copolymers are used in the base layer and most probably for improvement of barrier properties of films, and (8) present patent is limited to using 2-3 layered films. U.S. Pat. Nos. 4,876,146 and 4,956,209 which are hereby incorporated by reference.
All of the patents previously mentioned above, however, suffer from not having antimicrobial properties.
In the recent years, essentially growing trend is the use of various bioactive agents, including predominantly ecologically pure metal-containing biocides in polymer production industries for preparation of antimicrobial, antibacterial and antifungal polymer materials such as films, sheets, coatings, plastics, fibers, composits, etc. The number of patent publications in this field have increased in recent years. The following references have attempted to address antimicrobial films:
(1) U.S. Pat. No. 4,938,955, 1990 discloses an antibiotic resin composition comprising at least one antibiotic zeolite of which ion-exchangable ions are partially or completely replaced with ammonium ions (5-15%) and antibiotic metal ions (Ag+ of 1-15%), at least one discoloration inhibitor such as benzotriazole, oxalide, anilide, salicylic acid, phosphous, sulfur, etc. compounds and at least one polymer resin (this composition exhibits antibiotic property and does not discolour with time, and can be employed to form a variety of products which require antibacterial and/or antifungus properties);(2) Transparent bactericidal multilayer sheets with haze <5% comprise a crystalline thermoplastic resin containing 0.05-5 phr granular zeolite containing bactericidal metal ions in a sheet comprised polypropylene containing 0.5% Bacterikiller BM 103 (zeolite A containing 3.5% Ag) [JP Pat. 04,275,142 (1992), Chisso Co., Japan]; (3) Antibacterial polyolefin compositions with inhibiting effects on the growth of bacteria and moulds contain polyolefins and 2-pyridinethiol 1-oxide and its metal (Zn) salts or other organic biocides (polypropylene 100, 2-(4-thioazolyl) benzimidazole 0.25 and Zn 2-pyridinethiol 1-oxide 0.25 part were roll kneaded at 230° C. and then hot pressed at 220° C. to give a 2 mm sheet, which completely inhibited of the growth of Aspergillus niger, Penicillium citrinium, Chaetomium globosum, Aurebasidium dulllans, and Gliocladium virens at 28° C. for 28 days) [JP Pat. 04,270,742 (1992), Shinto Paint Co. Ltd., Japan]; (4) Antibacterial heat-resistant polyolefin compositions comprising polyolefins (polypropylene)100, bactericidal metal ions (Ag, Cu, Zn and/or Sn ions supported on zeolites) 0.01-1.5, dimethylsiloxane oil 0.01-0.2, and aluminium borate whisker (9Al2O3.2B2O3) 0.01-0.1 part showed good antibacterial action as tested against colon bacilli [JP Pat. 04,363,346 (1992), Tonen Kakagu Kk., Japan]; (5) JP 04,13,733 (1992) discloses antibacterial films for packaging chemicals and food which were prepared by treating one or two surfaces of films containing aluminosilicic acid salts with electrical corona (a composition containing 2 parts zeolite A (Ag content 6.7%, NH4 content 0.5%) and polyamide (6-nylon 66 copolymer) were together extruded and exposed to electrical corona for 0.2-10 s to give an antibacterial film with good adhesion to ham, versus poor adhesion for the film not treated with said corona); (6) U.S. Pat. No. 5,614,568, 1995 (Mawatari, M., et al., Japan Synthetic Rubber Co., Ltd., Tokyo) claimed an antibacterial resin comprising (A) 100 parts by weight of aromatic alkenyl resin, specifically styrene resin, (B) 0.01-30 parts of an inorganic metal compound or a porous structure substrate which has been injected to ion-exchange with a metal ion selected from the group consisting Ag, Zn, Hg, Sn, Pb, Cd, Cr, Co, Ni, Mg, Fe, Sb and Ba, and (C) 0.01-30 parts of a polyethylene comprising —COOH, —COOM(salts), —OH, —COOR, and epoxy, anhydride and amine functional groups, a polypropylene comprising said selective functional groups with molecular weight 10000-30000; (7) Japan Chem. Ind. Co. (JP Pat. 09,176,370, 1997) discloses an antimicrobial injection-moldable polypropylene composition showing no discoloration or degradation during processing, storage and uses contain 0.2 phr of liquid paraffin, 1.0 phr of the mixture of inorganic compounds Ag0.15Na0.5H0.35, Zr2(PO4)3 and Mg0.7Al0.3O1.15 which was used as an antimicrobial agent; (8) Polyethylene terephthalate films coated with thin Ag, Cu and Ti-layers by sputtering treatments have high antibacterial activity. The reducing in bacteria values of almost 100% were determined by the SEK Shake Flask Method and the Contacted Film Method [S. Kubota, et al, Bakin Bobai, 25 (7), 393 (1997); Chem. Abstr., 127, 122386s (1997)]; (9) Tokuda, et al, [JP Pat. 09,136,973, 1997] describes bactericidal packaging films comprising thermoplastic resins or blends on the base of PE, PP, PVC, polyesters and/or PS and calcined powder ceramics containing 40-60% of SiO2, 20-30% of Al2O3, 4-8% of ZnO, 2-5% TiO2 and 0.1-1.0% Ag or Cu salts as an antibacterial agent (these films were prepared by mixing above ceramics with said polymers and forming into films or by spreading or printing above ceramic-containing resins on resin base films); (10) JP Pat. 09,123,264 (1997) discloses antibacterial decorative sheets and manufacture of decorative moldings (these sheets were prepared by shaking colored base sheets with thermosetting diallyl phthalate resin composition containing 0.5% of Ag/Zr phthalate, Ag tripolyphosphate, Ag hydroxyapatite, and/or (Ag/Ca)3 phosphate. A printed paper sheet was hot pressed with a moldable polymer composition to form a waterproof pan for bathroom uses); (11) Bactericide-containing abrasive agents and resin moldings for video and arcade games comprise a thermoplastic resin (98% of polycarbonate) incorporated with fillers (1%) and bactericides (Ag-containing zeolite, Bactekiller) or bactericide-treated powders (1%) [Sumitomo Elect. Ind. Ltd., JP Pat. 09,77,880, 1997]; (12) JP Pat. 09,77,042 (1997) releases to antimicrobial synthetic resin containers for preserving drinking water (this container is prepared using synthetic resins with Ag-containing glass particles that release adequate amount of microbiocidal silver ions (Ag+) into the water where growth of bacteria or fungi in the drinking water is prevented by these ions); (13) JP Pat. 09,002,517, 1998 [Taisho Pharmaceutical Co. Ltd. (Tokyo, Japan)] discloses a process for making a bottle and cap with antibacterial properties on their inner contact surfaces. Antimicrobial zeolite power (1 to 5% by weight) containing microbiocidal Ag, Zn and Cu ions is mixed with thermoplastic resins such as ethylene-vinylacetate copolymer, polypropylene and polyethylene (the zeolite is dispersed throughout the bottle and is present on both inner and outer surfaces and can also be used for both cap and membrane seal); (14) Polypropylene plastic table wares contain an antimicrobial agent (Amenitor) (JP Pat. 09,108,084, 1997); (15) Bactericide power (Bactekiller) or bactericide-treated power containing adhesive agent and resin moldings for video areade games were described (Chem. Abstr., 127, 35460t, 1997); (16) Silver (Ag)-zeolite antimicrobial agents for protection of the plastic films from various microorganisms were manufactered by Michubusi Co. Bactericide ceramic power containing 0.1-1.0% Ag or Cu, 2-5% TiO2, 4-8% ZnO or MnO2, 20-30% Al2O3 and 40-60% SiC or SiO2 was recommended to use in the varoious thermoplastic composition (polyolefin, polystyrene, polyesters, etc.), resins and binders [T. Ishitaki, High Polym. Japan, 39(10), 744 (1990); Y. Kajiura, Jidosha Gijutsu, 51(5), 34 (1997); JP Pat. 09,136, 973 (1997)]; (17) Antimicrobial activities of some new coordination polymers were also discribed by Patel, et al. [B. Patel and M. Mohon, J. Polym. Mater., 13(4), 261 (1996)].
However, all these publications are related to the preparation and use of various antimicrobial polymer materials including non-orientated and non-multilayered polymer films, sheet, etc. containing bioactive metal ions. Thus the above patents describe inventions are essentially different from the present patent invention which is concerned with preparation of semi- and biaxialy oriented and multilayered antimicrobial thin films containing Ag+-containing polymeric bioactive agent only in the skin layer and having high physico-mechanical, thermal and antimicrobial properties. Another distinctive feature of these films is possibility of their use in the food packaging applications, where anti-fogging properties are required.
Several Firms such as Taisho Pharmaceutical Co. Ltd. (Tokyo, Japan), Kanebo Chemical Industries, Ltd. (Osaka, Japan), M. A. Hanna Company (USA, Neutrabac™ Antibacterial Masterbatch), Wells Plastic Ltd. (Staffordshire, UK), etc. have already started to manufacture organic and inorganic antibacterial agents and various antimicrobial Masterbatches for use in thermoplastic polymer compositions.
Many organic and organoelement compounds having high biological activities are also used in polymer film-forming composition systems [Z. M. Rzaev, CHEMTECH, (1),58 (1976); Z. M. Rzaev et al., England Pat. 1,270,922 (1972); U.S. Pat. No. 4,261,914 (1981); U.S. Pat. No. 4,314,851 (1982); Z. M. Rzaev et al., Bioresistant Organotin Polymers, Chemistry, Moscow, 1996 (Russ.)]. Thus, (1) “ICI Biocides” Firm (UK) prepared and patented new water soluble biocides on the base of isothioazolione useful for the effective preservation of polymer resins, specially aqueous-based paints from bio-destruction with microorganisms in the stage of synthesis, storage and uses of these materials [C. L. P. Eacoff, Orient. J. Oil and Colour Chem. Assoc., 74 (9), 322 (1991)]; (2) Polen Kagaku Sangyo K.K. [JP Pat. 09,169,073, 1997] discloses antibacterial and antifungal sheets laminated with low expanded olefin polymer (such as HDPE) compositions containing 0.1-1.0% 2-(4-thioazolyl)benzimidazole as an antibacterial and antifungal agent showing good deep drawability; (3) Antimicrobial rubber articles contain ammonium salt of chlorohexidine as an antimicrobial agent [UK Pat. 8,919,152 (1990)]; (4) Biocide Cl-containing polyketones having antibacterial activity against selected yeast, fungi,—and bacteria were prepared by Fiedel-Graft [Friedel-Craft] reaction of o-cresol with chloroacetyl chloride, dichloromethane and dichloroethane in the presence of anhydrous AlCl3 as a catalyst in nitrobenzene as solvent [B. T. Petel, et al, Orient. J. Chem., 13 (1), 83 (1997); Chem. Abstr., 127, 136122q (1997)]; (5) Polyethylene four-layered film was coated with mixture of allyl isothiocyanate (as a biocide), polyfunctional isocyanate, polyols and dibutyltin laurate (as a catalyst) to give a multilayered film with polyethylene outer layer having antibacterial activity [JP Pat. 09,151,317, 1997]; (6) Matsukawa Electric Works, Ltd. (Japan) was disclosed a method of preparing plastic table wares (plastic bowl) containing antimicrobial agents (Amenitop) by moulding. The core potion is formed with a polypropylene resin and this is coated with another polypropylene containing a said antimicrobial agent; (7) Kyowa Co. Ltd. [JP Pat. 09,135,716, 1997] patented the gas-permeable and antimicrobial bags for the medical application. These bags were prepared from cushion bases consisting open-celled polymer foams and bactericide-containing hydrophobic noncircular fiber; (8) p-Hydroxy butylbenzoate [JP Pat. 63,173,723 (1988)], 2-(4′-thiazolyl)-benzimidazole [U.S. Pat. No. 4,008,351 (1977)], Pt-vinylsiloxane complex [JP Pat. 04,202,313 (1993)], polymeric iodine complexes [U.S. Pat. No. 3,907,720 (1975), phosphate esters [U.S. Pat. No. 3,888,978 (1975), U.S. Pat. No. 3,991,187 (1976), U.S. Pat. No. 4,661,477 (1987), U.S. Pat. No. 4,935,232 (1990)] and 2,3,5,6-tetrachloromethylsulfonylpyridine (for preparation antibacterial styrene type resin compositions) [JP Pat. 07,82,440 (1995)] have also been recommended for use as bactericide and antimicrobial agent in the various polymer compositions, film and sheets.
There are a number of patents disclosing various polymer composits, thermoplastic fibers, sheets, coatings, films, etc. having biological activity toward different type of microorganisms [Shima et al., U.S. Pat. No. 4,000,102, 1976; Dell et al., U.S. Pat. No. 4,584,192, 1986; Fink et al., U.S. Pat. No. 4,751,141, 1988; Gillete et al., U.S. Pat. No. 5,152,946, 1992; Grighton et al., U.S. Pat. No. 5,246,659, 1993; 5,104,306, Apr. 14, 1992]. For example, (1) U.S. Pat. No. 5,178,495, 1993 discloses a polymeric film with biocide. A multi-ply film has been developed that includes a biocide in at least one the film layers. Said biocide mixed with the thermoplastic prior to extrusion of the sheet. This sheet with biocide can be used to construct water containment facilities for drinking water, fish farms and industrial use and can be used as a covering for water tanks or equipment in environments that promote microbial growth at the surface of the film; (2) U.S. Pat. No. 5,777,010 1998 (Nohr R. S., et al., Kimberly-Clark Worlwide, Inc., Neenah, Wis.) discloses melt-extrudable composition containing antimicrobial siloxane quaternary ammonium salts. These compositions which includes a thermoplastic polyolefin and a siloxane quaternary ammonium salt additive. Upon melt extruding the thermoplastic composition to form fibers and non-woven webs, or other shaped artides, the surfaces of such shaped articles exhibit antimicrobial properties. (3) Early, antimicrobial siloxane quaternary ammonium salts were patented [U.S. Pat. No. 5,567,372, 1994 and U.S. Pat. No. 5.569,732, 1994] and published [ Nohr R. S., et al., J. Biomed. Sci., Polym. Ed., 5(6), 607 (1994)] (U.S. Pat. No. 5,567,372, 1994 discloses a method of preparing a non-woven web containing antimicrobial siloxane quaternary ammonium salts); (4) U.S. Pat. No. 5,527,570 [Addeo, A., et al.,1996, Centro Sviluppo Settori Impiego SRL, Milan, Italy)] relates to a multilayer and multifunctional packaging elements having high-absorption activity toward aqueous liquid substances as well as barrier properties toward gases such as oxygen and carbon dioxide are prepared by thermoforming (Each layer comprises a polymeric thermoplastic material. Intermediate layer of this packaging element may also contain antibacterial agents); (5) U.S. Pat. No. 5,142,010, 1992 (Olstein, A. D. et al., H. B. Fuller Licensing & Financing Inc., Wilmington, Del.) discloses polymeric biocidal agents containing carboxyl groups, fluorene substitute and alkyl C1-20 groups, and any bioactive naturally occurring amino-acid chain (the resulting polymers are disclosed to be useful in any variety of applications requiring an antimicrobial agent or an active sanitizer or disinfectant including films, coatings and adhesives, as well as also being useful in medial, food preparation and personal care product applications; (6) Describes an antimicrobial film-forming compositions containing bioactive polymers (homo-, co- and terpolymers of monomers containing pyran groups) having pendant pyran groups [Greenwald R. B. et al., U.S. Pat. No. 5,108,740, 1992, Ecolab Inc., St. Paul, Minn.] (this publication describes a liquid composition that yields an abrasion resistant polymeric film on a surface that provides extended protection from microbial growth through slow release of a potent antimicrobial agent).
As evident from the above described patent publications, there is relatively small number of patent publications describing polyolefin based, in particular, mono- and biaxially oriented polyolefin based films, and all of patent publications suffer from one or more of the following properties: not being multilayered and oriented polyolefin non-opaque films, not being heat-sealable; not having antimicrobial properties using thin films containing Ag+-containing polymeric bioactive agent only in the skin layer, not having antifogging properties.